Blender for Architecture
I think @atomicbezierslinger might be correct, but I think Blender can be great for architectural renderings, but not necessarily designing. There are plugins that add Architectural Desktop-like features, but Blender is more like Maya than AutoCAD.

Two good resources to see what's capable in architectural rendering in Blender are: Blendswap and Blender Artists (for example: this recent rendering posted by the artist)